1. Field of the Invention
The present invention relates to boots for alpine skiing of the type which comprises an upper surrounding the lower leg of the skier, and a rigid shell base on which the upper is mounted.
2. Description of Relevant Information
Alpine ski boots are generally made of molded plastic material, and comprise a shell base surrounding the foot and an upper surrounding the lower leg of the skier. The upper comprises a cuff and a rear spoiler. These portions of the upper may be journalled, if desired, on the shell base around a transverse journal axis. A journal axis need not, where necessary, be physically present but the upper must be able to flex with respect to the shell base at least to certain degree, depending upon the conditions of use, so as to form the equivalent of a journal.
The general direction in which the upper extends called for reasons of simplicity, "the axis of the upper", is inclined frontwardly (with respect to a vertical axis passing through the shell base) by a certain angle known as the "advancement angle". From this advancement angle the boot must be constructed so that the skier can flex his leg frontwardly along a flexion angle. This advancement angle can be varied around an average value, depending upon the given circumstances of use because the upper can be journalled on the shell base. If the skier is often flexing the boot beyond the advancement angle, it is desirable to increase the advancement angle. In alpine skiing the optimal advancement angle is on the order of 13.degree.-20.degree. and sometimes may even reach 25.degree., while for the touring skier, an angle of 8.degree.-15.degree. is generally considered optimal. Furthermore, depending upon the type of skiing practiced and the state of the snow, the skier will require more or less flexibility in journalling the upper on the shell base, i.e., the skier will require greater or less difficulty in sweeping his leg forward from the advancement angle. Thus, one needs a sufficiently high stiffness for competition on hard snow or ice, and sufficient flexibility on powder snow and during descent so as to support oneself and to arrange one's muscles to achieve a flat skiing position.
These considerations are manifested by the need more and more skiers have for boots which not only have an average advancement angle corresponding to their personal criteria, but which also have means for controlling the flexion of the upper on the shell base. This allows the the boot to vary the resistance moment of the upper opposing the flexion of the leg of the skier on the upper, thereby increasing the comfort and safety of the user.
Numerous attempts have been made to satisfy these requirements by apparatus which control the flexion of the boot. For example, French Pat. Nos. 2 100 490 and 2 416 661, disclose a shock absorption apparatus having a simple or double effect spring anchored between a central point situated at an elevated position on the front of the cuff and a central point situated towards the front of the foot on the rigid shell base or integral with the rigid shell base. However, these apparatus have an unattractive appearance, they are very cumbersome and are exposed to shocks and to anything the skier encounters during movement of the ski, thereby increasing the probability that the boot will become caught on objects the skier encounters. As a result, these apparatus present a possible danger to the skier and their reliability is entirely uncertain.
French Application No. 2 278 280 discloses an apparatus which acts as an accessory to the boot and partially performs the desired functions noted above. However, it requires removable linkage elements between the rigid shell base and the cuff. The cuff pivots with respect to an element of the boot, which in the field of the present invention would be called a rear spoiler, because the entry into the boot occurs from the front. This apparatus placed at the rear of the boot, only flexes by virtue of its elasticity because this boot has no journal defining a transverse axis around which the the cuff can pivot on the rigid shell base. This solution is thus foreign to the present technical domain of the present invention which relates to an upper which is journalled on a shell base, and which opens rearwardly to permit the skier's foot to enter the boot.
These two apparatus discussed above perform their functions only in a longitudinal vertical plane or one which is approximately in a longitudinal vertical plane. As a result, these apparatus do not affect the flexion of the boot at the flexion fold or the instep of the boot.
Similar apparatus are described in German Application DE-OS No. 30 44 052, which discloses a spring anchored at the two points discussed in the applications discussed above, and French Application No. 2 495 901, in which where a double flexion blade is also anchored at the two end points noted above in the other applications.
Another solution is proposed by French Application No. 2 342 040. In this application an elongated support element is described which is fixed at one end on the front abutment of the binding of the boot and has at its other end a projecting portion which is introduced between two buckles whose position on the boot is adjustable, so as to limit the advancement position of the upper of the boot.
French Pat. Nos. 2 096 248 and 2 103 171 disclose a boot comprising compression or tension springs positioned in the longitudinal direction between the cuff and shell base and attached to pivot at their ends or points of application on these elements, directly or by means of an intermediary element. The former patent, however, is directed to the adjustment of the advancement angle of the upper and not to flexion control. Further, this device is apparently considered an accessory, and its elements are made of rubber serving to absorb excessive frontward pressures. The latter patent is not directed to the control of flexion, but only to absorbing shocks so as to obtain a soft transmission of the shocks between the foot and the ski. These springs serve to resist flexion of the foot, but being interchangeable, any modification of the resistance force necessitates a disassembly and reassembly of the apparatus, which is practically impossible on site.
In all of these cases the solutions proposed, whose number alone illustrates the importance and difficulty of the problem, have at least one and generally a number of notable insufficiencies in common: poor or doubtful effectiveness; complexity, which leads to prohibitively high costs; the ability to limit only the maximum advancement or flexion of the upper; and the adjustment of the apparatus can be made only once before skiing, which results in a loss of progressiveness as the leg flexes and which is inadequate under actual conditions.
An important step was made in overcoming these disadvantages in French Application No. 84.13152. This patent discloses an apparatus on the ski boot which permits flexion of the upper with respect to the shell base. The apparatus is effectively adjustable, depending upon the needs of the skier, before beginning skiing. Further, the apparatus has real progressiveness during skiing, which is controlled by the instantaneous conditions of use, and prevents extreme flexions damaging to the leg as a result of the anatomy of the leg. In addition, the apparatus absorbs shocks from the flexional forces via its elastic return, which is also sufficient for forces of lesser amplitude. In this apparatus, a flexional element positioned in the longitudinal direction between the shell base and the cuff is connected at one end to one of these elements and slidingly engages a ramp carried by the other of these elements. An adjustment element is provided to vary the flexional performance of the boot in a ratio which can be, for example, 1 to 2. This very high performance boot is very technically complex and an aesthetic integration of the apparatus into the general configuration of the boot is only barely achieved resulting in a substantial increase in production costs. Also, the boot appears to be designed for use by skiers who are very demanding, who have a very high skill level, and for whom price is not the primary consideration.
Therefore, there is a need for a boot whose flexional characteristics can be adjusted, depending upon the needs of the skier, before skiing, and which varies the resistance to flexion instantaneously depending upon conditions of use. Further, there is a need for a boot that also limits flexion that would be harmful to the leg, and which, at the same time is simpler in construction, and therefore, lower in cost, so as to make it available to a wider segment of the public.